The substantive rank of captain is typically held by officers captaining starships. Officers of this rank also sometimes serve in other capacities, such as in command of starbases or divisions of support personnel (such as JAG officers or members of the Starfleet Corps of Engineers), or as members of experimental engineering programs.

According to the rules of naval parlance, a person of any officer rank may be addressed as captain if they are assigned as sole commanding officer of any starship. Captains may also be awarded provisional (brevet) ranks or field promotions to be accorded the title of captain.

The substantive rank of captain is typically held by officers captaining starships. Officers of this rank also sometimes serve in other capacities, such as members of experimental engineering programs.

According to the rules of naval parlance, a person of any officer rank may be addressed as captain if they are assigned as sole commanding officer of any starship. Captains may also be awarded field promotions to be accorded the title of captain.